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MrSeb writes "DARPA has begun development of a wireless communications link that is capable of 100 gigabits per second over a range of 200 kilometers (124mi). Officially dubbed '100 Gb/s RF Backbone' (or 100G for short), the program will provide the U.S. military with networks that are around 50 times faster than its current wireless links. In essence, DARPA wants to give deployed soldiers the same kind of connectivity as a high-bandwidth, low-latency fiber-optic network. In the case of Afghanistan, for example, the U.S. might have a high-speed fiber link to Turkey — but the remaining 1,000 miles to Afghanistan most likely consists of low-bandwidth, high-latency links. It's difficult (and potentially insecure) to control UAVs or send/receive intelligence over these networks, and so the U.S. military instead builds its own wireless network using Common Data Link. CDL maxes out at around 250Mbps, so 100Gbps would be quite a speed boost. DARPA clearly states that the 100G program is for US military use — but it's hard to ignore the repercussions it might have on commercial networks, too. 100Gbps wireless backhaul links between cell towers, rather than costly and cumbersome fiber links, would make it much easier and cheaper to roll out additional mobile coverage. Likewise, 100Gbps wireless links might be the ideal way to provide backhaul links to rural communities that are still stuck with dial-up internet access. Who knows, we might even one day have 100Gbps wireless links to our ISP."

It should be doable, providing two conditions are allowed:1. The equipment may be ridiculously expensive (No problem: Around half the US government's budget goes to defence).2. It'll need to be such high (analog) bandwidth, it'll not comply with any spectrum or power regulations, anywhere (No problem: If you're invading a country, you don't need to be overly concerned with obeying local laws, and even occupiers get some leeway).

Looks like someone needs to educate this dumbshit about the difference between discretionary spending (of which defense definitely IS) and non-discretionary (as in you will break a law if you don't make that payment).

And you will forgive a foreigner for not fully understanding the intricacies at which the US government spends/wastes money. We do it better than anyone else in the world, naturally. Those socialist europeans don't waste money nearly as well as we do, and they are a bunch of socialists for go

1. The equipment may be ridiculously expensive (No problem: Around half the US government's budget goes to defence).

Dude, 30 years ago the idea of a hard drive with a "gigabyte" of capacity was something ridiculously expensive, taking up football-field sized buildings, and everyone thought it'd be a really dumb idea anyway; Tape would be better for storage. Now I can get 64GB of storage to fit on my index finger and it's only a fingernail's thickness. The argument of "it'll be ridiculously expensive" dies over a long enough time span.

It'll need to be such high (analog) bandwidth, it'll not comply with any spectrum or power regulations, anywhere.

Ding! We have a winner. Though, not for the exact reason you're thinking. It could in fact work, and even within certain power requirements. But it'll never get regulatory approval, and it has nothing to do with technical requirements, but the fact that (at least if we're talking about the United States) the people in charge are paid large amounts of money to maintain the status quo. Remember that price fixing scandal for digital TV when the FCC fucked up the transition so badly Congress had to intercede... three times? Yeah... what ever happened to them? Oh right... the FCC made billions, the corporations made billions... the taxpayers lost many billions, and... oh right: They were fined, uhh.. less than a penny on the dollar against their profits.

Every attempt to give the general public access to high speed digital communications for cheap has been blown out of the water faster than you can say "Republican in a bathroom stall at an airport."

"30 years ago the idea of a hard drive with a "gigabyte" of capacity was something ridiculously expensive,...Now I can get 64GB of storage to fit on my index finger and it's only a fingernail's thickness. The argument of "it'll be ridiculously expensive" dies over a long enough time span."

Radio technology is not much older and much more developed than hard drive technology. There is no indication whatsoever that some near future technological advancement will make high power, high frequency technology an o

This is so much pie-in-the-sky bullshit I can't even believe it. I hear about this kind of thing year after year, and it never happens.

This is DARPA, a company for whom "aim at the sky" is more of a directive rather than a metaphor. Some of there other work includes flying tanks, passive radar systems, stealth ships, onion routing, and wide area interconnected computer networks. Most of it doesn't work, of course... but when it does, we get something no one else would have bothered developing.

As someone who is currently working on a DARPA program (and having worked on another one in the past), there is a term that is commonly bandied around in academic circles... "DARPA hard". DARPA does not fund incremental research that improves something by 2X. They are always on the lookout for funding truly groundbreaking and innovative concepts and their call for proposals always have ridiculous aims. It isn't very often that a team is able to satisfy all the deliverables for a DARPA program, but even in t

I don't know why I'm responding since you're AC and won't see it, but if someone else is wondering the same thing, you can hear an FM radio broadcast for a couple hundred miles in some conditions. That radio station has a 50,000 watt transmitter, but the power drops off inversely. By the time it reaches your property it's only milliwatts.

An FM broadcast antenna is indeed directional, in the vertical plane. It flattens out the signal from a sphere so that most of the power is on a level plane. That's how an antenna creates gain. On the other axis it is most often omnidirectional. That 50KW is ERP (Effective Radiated Power), the transmitter is likely only putting out about 10KW.

An FM broadcast antenna is indeed directional, in the vertical plane. It flattens out the signal from a sphere so that most of the power is on a level plane. That's how an antenna creates gain. On the other axis it is most often omnidirectional. That 50KW is ERP (Effective Radiated Power), the transmitter is likely only putting out about 10KW.

Close but not quite. EIRP is where you start; with an idealized transmitter that radiates power equally in every direction. ERP is calculated based on the energy of the antenna's main lobe, which for an FM transmitter typically looks like a small circle and a long oval connected at the antenna. The difference in power between the EIRP model and signal strength in the main lobe of the antenna is the antenna's gain, which is where your ERP calculation comes from. A transmitter with an antenna having 6dB of gain means it can transmit at 10KW and have an equivalent signal strength (in the main lobe) to an ideal antenna radiating in all directions at 40KW.

About as close as you'll get is a dipole [wikimedia.org] but then you still end up with more of a doughnut. [wikimedia.org]

Just about any antenna can be modeled as a dipole. For example, an AM broadcast antenna (AKA a vertical) is just a dipole where the tower is one side and the earth is the other. Actually on an AM tower there is a lot of copper strap laid out radially underground from the base of the tower and the whole tower is electrically insulated from the ground. Same thing with a mobile antenna on a car, the s

With this kind of bandwidth, fleets of tele-operated ground vehicles will become reality. Today there isn't enough bandwidth today to send back video, location, and other sensor info to intelligently navigate more than a vehicle or two. This will save many lives. Bravo DARPA!

You can buy 60GHz units that are from the 1Gbps to 2Gbps transfer rates, depending on lots of different factors. There may be faster licensed units then that, but I'm guessing the price would be insane. A 100x increase in bandwidth doesn't sound impossible if you have the free air space and are willing to spend the power.

I am guessing that this only works because a huge amount of radio spectrum bandwidth is allocated per user. There probably is no actual method of scaling this up for general-purpose usage. The last line of the OP seems beyond speculative.

To achieve that kind of bandwidth the signal is probably going to have to be very narrow and so you can achieve greater throughput using spacial distribution as well and channel distribution. Some of the higher end WiFi systems already do this kind of bandwidth improvement by using beam steering technology to logically switch between multiple clients, the same kind of technology is also used in satellite systems where the same frequencies are reused many times between the ground and transponder.

Spacial distribution, like "channel hopping" to avoid interference? That helps with moving transmitters/receivers, but not within a static local area. In the end, for any given area covered by a transmitter, the frequency availability will be the hard cap on the shared bandwidth for that area. If 10k people in a given coverage area all want to download large files at 100 Gbps, all the trickery in the world won't increase that cap.

Somewhere, someone must have a simple rule-of-thumb for this sucker, like how

No spacial distribution like using beams 1 degree wide to turn a 100Gbps per 40MHz technology into a 36,000Gbps per 40MHz technology over the area covered by a synthetic array. Of course it doesn't quite scale like that because you have to spread out what part of the 40MHz your clients use so that clients in close proximity aren't using the same frequencies at the same time, but it's fairly amazing just how much bandwidth you can fit into an area using beam steering versus using a simple monopole. Currently

Actually, I'm guessing it could work for commercial usage if all the links were site-to-site links achieved with some kind of directional antennae (perhaps using conic-section backplates), so that they mostly don't pollute the airwaves all around them very much. In other words, an ISP (or any medium-to-large company) could set up a directional antenna in $smalltown and aim it at their other directional antenna in $wellconnectedlocation, creating a high-speed link between the two sites, without running fibe

The problem that was already addressed is the curving of earth, because it can be overcome with height. Let's sustain that increasing the altitude of your dishes will allow greater distance without the sphere's shape interfering, you still have all of the factors associated with those heights: weather, cost of getting there, service, general maintenance.

Maintenance: How easy is it to remove ice? Snow? What about the cost of maintaining the tower?

Service: What do you do when you can't communicate with the unit, and you've ruled out everything except the cable between the unit and it's nearest point of contact?

Cost: This is a broader issue than maintenance, because it allows for not owning the tower/building. Tower space is premium, building roof-tops are premium, labor to install, service, or repair is EXTRA premium. Not only do you need guys willing to climb 200+ feet, but they need to be technically capable. http://www.midweststeeplejacks.com/ [midweststeeplejacks.com] charges no less than $250/hr.

Weather: Why don't you see point-to-point connections on towers that are 200ft up on towers? Because the bandwidth requires very high frequencies, and those frequencies are very susceptible to any movement caused by wind. I've seen a gentle breeze (on the ground) turn a wireless link from -45 dbi to -60. Let's not forget rain and snow.

The only good ways to mount an antenna or dish at a height, and ensure reliability, are with a very large antenna (think something with 3 or 4 legs and covering at least 400 feet^2), or a building.

The problem that was already addressed is the curving of earth, because it can be overcome with height. Let's sustain that increasing the altitude of your dishes will allow greater distance without the sphere's shape interfering, you still have all of the factors associated with those heights: weather, cost of getting there, service, general maintenance.

Maintenance: How easy is it to remove ice? Snow? What about the cost of maintaining the tower?

Service: What do you do when you can't communicate with the unit, and you've ruled out everything except the cable between the unit and it's nearest point of contact?

Cost: This is a broader issue than maintenance, because it allows for not owning the tower/building. Tower space is premium, building roof-tops are premium, labor to install, service, or repair is EXTRA premium. Not only do you need guys willing to climb 200+ feet, but they need to be technically capable. http://www.midweststeeplejacks.com/ [midweststeeplejacks.com] charges no less than $250/hr.

Weather: Why don't you see point-to-point connections on towers that are 200ft up on towers? Because the bandwidth requires very high frequencies, and those frequencies are very susceptible to any movement caused by wind. I've seen a gentle breeze (on the ground) turn a wireless link from -45 dbi to -60. Let's not forget rain and snow.

The only good ways to mount an antenna or dish at a height, and ensure reliability, are with a very large antenna (think something with 3 or 4 legs and covering at least 400 feet^2), or a building.

You sound like someone who has never looked at a communication tower, much less installed and used equipment on one.

I run a WISP and have equipment dangling hundreds of feet in the air. With proper planning, amazing results can be achieved. Weather is a factor over 6Ghz but, once again, this is not a problem with proper planning.

Actually, I work for a WISP. I've done my share of climbing 60-100ft antennae to install or repair the equipment we've got up there, and I've experienced the tower sway at that low height. There are a few other locations where there are things mounted around 250 or so, but I haven't tended anything that high up on a flimsy structure. Lots of things are hanging out on top of buildings that are 120-300ft, but most of those installations have enough structure to remain pretty rigid.

I think to achieve a 120-mile range, you're going to need towers at both ends. A quick back-of-the-envelope calculation suggests that if one endpoint is on the ground, the other would have to be elevated about three miles, at which point fiscally speaking you may just about as well put it in low earth orbit.However, I suspect the "120 mile" figure is probably what they figure the equipment would support GIVEN line of sight as a base assumption. In practice, dealing with topography and whatnot, you're prob

I had already heard of airborne wireless base stations being deployed for the U.S. military (possibly reported here a few years back?), so this actually doesn't sound as crazy as you think. As I recall, they have some blimps or zeppelins geared up to do this sort of thing. If not, however, who says you need line of sight? I mostly stick to software, so I'm about as far from an expert as you can get when it comes to radios, but even I know that AM radios can be picked up at these distances, particularly at n

I mostly stick to software, so I'm about as far from an expert as you can get when it comes to radios, but even I know that AM radios can be picked up at these distances

It depends on the frequencies. Short wave and AM radio can be heard around the world because the waves bounce off the stratosphere. The term for this is ":atmospheric skip". Other frequencies, such as TV and FM radio, are limited to line of sight, with the earth's curvature being the limiting factor -- the waves don't skip, they keep going i

Well, if Slashdot ever bothered linking to the original article [darpa.mil], you'd see:

The goal is to create a 100 Gb/s data link that achieves a range greater than 200 kilometers between airborne assets and a range greater than 100 kilometers between an airborne asset (at 60,000 feet) and the ground.

If this idea actually works on a drone, that means it's both lower power and physically compact. No giant dishes, no enormous power budgets. That makes it far more likely that it would be useful in a consumer context.

Something tower-based with typical military power requirements wouldn't nearly as interesting. Sure, it could work, but...

"What was that sizzling sound?""Line noise.""Why is there a dead bird lying on the ground outside?""Like I s

Um...you dont need Line of Sight. It helps, but its not required.HAM operators have been talking around the globe for years.I pick up radio stations (AM and FM) from Atlanta in Macon, and from Tulsa in OKC regularly, and I'm definitely over the horizon in both cases, no matter how tall those broadcast antenna are.

The key part of the transmitter is power, and it's the easiest way to extend the range.But the reciever matters too: the key step in a radio is the quality and design of the circuitry. My KIA car r

And if you manage high-bandwidth 125-mi range, the next step is obvious - a constellation of LEO (200-500mi altitude) satellites serving as a nearly-untouchable* backbone for the theater-WAN.

*ok not for peer-level opponents, but I'm pretty certain that a peer-level conflicta) will not be based on UAVs for long (my biggest concern about UAV-dependence of our forces), andb) will be over one way or another pretty fast if it's not going to turn SO nasty that any conventional force tech will be nearly irrelevant anyway (the not-so-comforting corollary that would invalidate my concerns above)

Actually, the next step is for the FCC to ban it under some vague and previously unknown test protocol as causing inteference to devices receiving the signal at -108dB. See also: Every attempt made to bring faster wifi to the masses so far.

If you're talking about the Clearwire 2.4GHz trial, that was correctly halted when it was proven that 80+% of the commercial GPS receivers in the test area were effectively jammed. It shouldn't necessarily be the case that licensed users are responsible for negligible interference on adjacent bands, but the Clearwire trial was provisional on them being able to show that they could leverage those bands without affecting critical national infrastructure and they failed. That the failure was due to the failing

Yes, yes, and yes.One possible solution would be using a directional antenna. A tight beam to the "WAP". Also Jammers have a short life time. Jammers tend to put out a lot of RF. Even missiles like the AIM-120 have a home on jammer mode. If this seems like an issue then the HARM AGM-88 will be updated to home on those jammers. The US also now has a lot of old AIM-7 SARA missiles that could also be updated to be an anti jammer missile. What it comes down to is do you want a fast network that may more may no

It's difficult (and potentially insecure) to control UAVs or send/receive intelligence over these networks,

With this new development I'm sure terrorists with $100 worth of radioshack gear will love taking control of our drones at ludicrous speeds. Since the US are too fucking dumb to turn on authentication on their drone links

it's not the authentication that's the problem... it's that they're choosing to use telnet and/or the r-tools for it.

they also need to focus on beaming energy around, esp. that distance. By being able to beam energy around, they make it possible to provide remote support to forward lines esp. with tanks, FOBs, and even ships at sea.

With wireless links of that capacity, the competition for ISPs would be through the roof. For that matter, if the regulation allowed it, darknets may start forming (think Open wifi that doesn't connect to the regular internet). That's the best case, if setting-up a router made you a peer on a network of peers (all independently owned), there would be no ISP.